(i) Field of the Invention
This invention relates to a personnel transfer system. More particularly it relates to a personnel transfer device and a personnel transfer apparatus for the purpose of transferring personnel from a first vessel to a second vessel, or for rescuing personnel from a first vessel to a rescue vessel, at sea.
(ii) Description of the Prior Art
The most common personnel transfer apparatus for rescuing personnel at sea are lifeboats. However, in the case of severe storms which cause high waves, the use of lifeboats is rendered impractical, should the need arise. Lifeboats may be damaged by being thrown against the hull of the ship during launching, or may be swamped by the waves. Also, high waves and violent seas may preclude entering a lifeboat from the deck of the vessel. After launching, should it be successfully accomplished, wave action may swamp the lifeboat, or injure its occupants by throwing them about inside the lifeboat.
Enough experience has now been accumulated to demonstrate the limitation of escape equipment provided for personnel working on offshore platforms. Much of the past and present safety provisions have been biased toward providing escape craft supported at the sea surface, such as boats. This "floating lifecraft" fixation has been discredited as providing inadequate protection for personnel abandoning doomed offshore platforms.
Superficially, it appears that sturdily constructed and well-provisioned surface lifecraft, entered efficiently and launched successfully, is an effective means of preserving life. However, the violent storms destroying these platforms have claimed the lives of enough personnel to thoroughly discredit these surface crafts as havens of refuge for personnel. Of course, if the personnel can be removed from the platform, well in advance of developing life-threatening weather conditions, the problem would be solved. Boats and aircraft, employed in time, are quite effective in preserving life. It is the illusion that platforms are effectively designed to withstand the fury of cyclonic storms that has lead to the entrapment of personnel by their decision to ride out the danger of the storms. In the face of platform collapse, it is now evident that few lifecraft at the surface of the sea have been preserving a significant percentage of the lives of the personnel. Obviously, something is dreadfully wrong with the superficial assumptions that have been made to date by personnel seeking safety at the sea surface.
With safety proven non-existent at the surface of the sea, it has been suggested that refuge be sought entirely below the surface. Serious consideration has been given to the concept of transporting personnel to a location entirely below the surface. It has appeared that a system can be provided to transport threatened personnel a significant distance below the surface of the disturbed sea to provide dramatic increase for their chances of survival. Seemingly, all that was required was a change in conventional attitude to accept a submersible vessel for transporting personnel to a safe sea depth. It now appears economically chimerical to provide a life-support system for a completely submersible escape vessel.
A logical combination of the concepts embodied in a completely submersible lifecraft is possible. If a lifecraft form can be provided which places the majority of its bulk a significant distance below disturbed surface conditions while providing safe access to life support surface systems, the disadvantages of both prior systems can be eliminated.
Accordingly, means have been sought to support the use of lifeboats. In U.S. Pat. No. 4,365,579, patented Dec. 28, 1982, by Perez Jr., for example, a life survival capsule was provided of substantially spheroidal shape. The capsule had self-contained life supporting facilities and supplies for approximately 16 occupants. It was made of double-hulled construction and included a thermal insulating material between the hulls. Restraint devices were provided to prevent injury to occupants. Multiple entrances or exits, were also provided including an entrance from the interior of the ship on which it was mounted. Automatic and manual release devices were provided to free it from the ship to which it was attached. This patent suffered from the inherent deficiency that it was, in effect, merely directed to a lifeboat.
U.S. Pat. No. 4,522,144 patented Jun. 11, 1985 by Klem, provided a rescue system for a marine structure such as an offshore drilling rig or production platform which included an enclosed type lifeboat constructed to be supported onboard the marine structure by being releasably-suspended over free water from a single point or fulcrum. The fulcrum was located relative to the center of gravity of the lifeboat such that the lifeboat, in its suspended position, adopted a predetermined slanting orientation which it maintained substantially constant throughout its free fall when released from its suspension. This patent suffered from the inherent defiency that is was, in effect, merely directed to a lifeboat.
U.S. Pat. No. 4,627,821 patented Dec. 9, 1986 by Bradley et al, provided a rescue device for use with a helicopter which included a floatation ring large enough to surround several standing persons and a rigid, non-buoyant open decking capable of supporting those persons. A collapsible netting surrounded the deck and connected the floatation ring thereto. The floatation ring had sufficient buoyancy to support the whole device when in the water with the deck suspended below the water level and with several persons standing on the deck and which were partially-submerged. Supporting cables for use with a helicopter hoist were fixed both to the ring and to the deck so that when the device was lifted, the ring was held a predetermined distance above the deck. This patent suffered from the deficiency that its structure was not sufficiently rigid to protect persons being transported.
U.S. Pat. No. 4,773,887 patented Sep. 27, 1988 by E. T. Stepfanus, provided a rescue device for small boats. That rescue device included a rescue basket of open lattice work having a bottom wall with a high side wall inboard and a raised edge outboard. Rollers mounted to the side wall engage guide rails extending downward along the hull of the boat. A winch and cable system raised the basket from a submerged position in which the person being rescued could be easily maneuvered into the basket utilizing the buoyancy of the water, and a raised position in which upward travel of the rollers was limited by detents in the guide rails. Continued operation of the winch caused the basket to pivot around the rollers bringing side wall into a horizontal position generally level with the top edge of the boat. The person being rescued was rolled onto the side wall where aid could be administered during transport to the land or the victim can be easily brought completely into the boat. In this pivoted position, the bottom wall of the basket was substantially vertical so that the person being rescued could not roll overboard. A latch mechanism locked the rollers in the detents and the bottom wall of the basket may be cinched against braces by the winch to form a stable platform for transport of the person being rescued to land. This patent suffered the disadvantage of a complicated structure including movable portions which were not fail safe.
U.S. Pat. No. 4,781,144 patented Nov. 1, 1988 by O. P. O'Brien, provided an offshore evacuation system for drilling rigs or platforms. It included a launch structure for a survival craft. That structure included at least one support strut adapted to be pivotally attached at one end thereof to the platform superstructure and which carried at the other end thereof at least one support cradle for the survival craft. The cradle was rotatable between an upper position and a lower position. Means were provided for effecting rotation of the launch structure from said upper to the lower positions. A closed companionway lead from the platform accommodation unit to the loading position of the survival craft was in sealing relationship with the survival craft. This patent suffered the disadvantage of a complicated structure including movable portions which were not fail safe.
U.S. Pat. No. 4,822,311 patented Apr. 18, 1989 by J. W. Doerffer et al, provided a free fall, submersible life saving device for an offshore structure having a spherical pressure shell in a casing. The upper part of the device had a lifting frame and at least one manhole closed with a cover. The lower part had ballast, an anchor, and a windlass for the anchor rope having automatic control of the tension in the anchor rope. The device was launched by a catapult on the offshore structure for horizontal movement in free fall to the water surface, where it submerged and was anchored until resurfacing, by release of the anchor, for rescue. This patent suffered the disadvantage of a complicated structure including movable portions which were not fail safe.
Harness devices and nets are presently available for use with helicopters for lifting survivors from open water and winching them into a helicopter. Harness devices are only capable of lifting one person at a time and require the person to be conscious and able to put on the harness. Net devices have also been used for pulling survivors from water and have usually been of the so-called side-entry type. However, the existing side-entry net devices are extremely difficult to enter. The net folds in the water, and the survivor has to find the opening and disentangle it before entering. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
Most of the existing baskets are made from wires soldered together to give a mesh structure equipped with two gripping handles joined by their central section by means of a non-detectable connecting component provided with a hoisting eye. These non-flexible, non-collapsible baskets often cause excessive obstruction, which restricts their handling and storage. In addition, being metallic, they need constant maintenance to limit the intense corrosion to which they are subjected. They are furthermore very heavy and can undergo permanent deformation under the action of load and shock. They are usually made in one piece, and their repair requires renewal operation which cannot easily be carried out. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
A rolling net, e.g., a kind of an elastic lattice is also presently available, where one side of the net is fixed within the gunwale of a ship and the other is pulled up with a person in the net rolling up the side of the ship. The device is unfit for use in heavy sea. The device is not capable of being transported to the person, it is fixed to the gunwale and only made for life boats patrolling to a wounded person in calm sea. It is not intended for other uses, for example, for use on usual ships.
Another secure rescue basket is provided by Canadian Patent Number 1,224,676, patented Jul. 28, 1987. Prior rescue baskets usually comprised various forms, a circular basket structure having a grid or net bottom and a peripheral wall provided with buoyancy means, cushion padding etc., the basket being connectable to a lowering or retrieval wire, the other end of which being connected to a davit or crane structure onboard a vessel, a main platform--floating or the gravity type, a helicopter or the like. An inherent disadvantage of such structure was that the wire becomes slack due to the swell of the sea, whereby the wire, the connector--e.g., a hook, a swivel and the like, represents a potential danger for the person or persons in the rescue basket. The patented rescue basket was handled by means of a weighed wire. The guide for the wire on the rescue basket was provided in the form of a centrally extending tubular guide means, the guide means extending to a such height above the basket bottom that a slackening of the wire only will result in the wire bending outwardly and eventually hit the outside of the basket wall, without hitting personnel sitting in the basket. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
Another problem with the prior rescue baskets resides in cushioning the basket upon it being hauled-down onto the deck of a vessel. Many devices have been provided to give a shock-absorbing effect.
For example, Canadian Patent Number 535,577 patented Jan. 8, 1957 by A. S. Fletcher et al, provided a pneumatic shock-absorbing device comprising an inflatable, perforated bag and a membrane covering a performation in the bag and of lower breaking strain than the bag, whereby the bag will absorb a relatively violent initial impact without bursting, but will still retain sufficient air to afford continued cushioning after the initial impact.
U.S. Pat. No. 4,883,301 patented Nov. 28, 1989 by B. G. Pugh, provided an improvement in a personnel/cargo net having at least one spreader ring. That spreader ring was provided by a base spreader ring including top and bottom rings secured together in vertically-spaced relationship. A buoyant pad surrounded each of the top and bottom rings. At least one separate, fluid-containing, shock absorbing means was provided for absorbing landing- or collision-shock experienced by the base spreader ring. Such shock-absorbing means was located above the buoyant pad. This patent suffered from the deficiency that its structure was not sufficiently rigid to protect persons being transported.
A rescuing basket was also provided by U.S. Pat. No. 2,557,079, but it had many drawbacks. The person being rescued must climb into the basket over a stiff floating girdle and upon a shallow net with small meshes, where he will not be meshed and is therefore vulnerable in a storm and heavy seas. The basket was difficult to manage up the side of the ship and the friction seeks to overturn it, especially in heavy sea. Therefore the basket had to be suspended free and therefore needed a boom. Such a boom was a part of the device and the person can not be saved except when the person fell into the sea below the boom. If the boom was on the one side of the ship and the person fell into the sea on the other, the device was of no use.
A net device was proposed in U.S. Pat. No. 2,817,860 which issued to Fritz, on Dec. 31, 1957. This patent disclosed a net device having an open top with a floatation ring so that the main part of the net was suspended under water. This device is intended to rescue only one person at a time since during rescue the net was partially-collapsed and the netting bottom provided a kind of sling for the survivor. A problem also exists in the excessive swigning of the harness-net device in high wind conditions.
U.S. Pat. No. 4,678,446 patented Jul. 7, 1987 by Daham, provided a device for rescuing personnel from water comprising a crane positioned on a boat or other rescue structure and which included a horizontally- and vertically-movable crane boom. An elongated member was vertically-movable with respect to the crane boom, and a float was positioned beneath the elongated member for floating on the water. A net extended below the float, and means were provided for supporting the net from the elongated member. When personnel were in the water, the crane was operated to move the boom from an inboard position to an outboard position, and the elongated member was permitted to move downwardly with respect to the boom such that the buoyant means floated on the water. At this position, the net extended beneath the float in the water. The net was moved forwardly by operation of the boom (and/or the boat) such that the person was within the net. The operator then manipulated the boom to hoist the person on the rescue structure. This structure was said to be provided for scooping personnel out of the water without such personnel needing to assist in their own rescue. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
U.S. Pat. No. 4,610,635 patented Sep. 9, 1986 by Austevol, provided an arrangement for picking up personnel. It included a basket or container which was connected to a ship and which was adapted to be conveyed between a work position partially-submerged in the sea and a rest position onboard the ship. The basket was rigidly-connected to a boom which was rotatable about its axis so that the basket in the work position was movable in a vertical plane substantially parallel to the vertical side of the ship, and which was pivotable between the work position, in which it projected outwards substantially-horizontally from the side of the vessel and the rest position. This patent suffered from the deficiency that its structure was not sufficiently rigid to protect persons being transported. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
U.S. Pat. No. 4,294,331 patented Oct. 13, 1981 by R. H. Reynoir et al, provided an improvement in a system for escaping from an offshore drilling or production platform in an emergency situation which included a stable floating structure forming a safe haven anchored near but at a safe distance from the platform. In the old system an aerial cableway extended between the platform and the haven, and a personnel carrier was movable along the cableway. The haven was a semi-submersible structure for increased stability. The system included a buoyant floating haven anchored in a relatively fixed position near, but at a safe distance from, the platform, a downwardly inclined cableway extending above water from the platform to the haven and a personnel carrier suspended on the cableway for transporting personnel from the platform to the haven. In such system the haven was in the form of a self-propelled vessel, namely, a catamaran. Such a vessel, however, not only was expensive but was also subject to some degree of pitching and rolling in rough seas. Further the cableway was in the form of two parallel cables which had to be properly tensioned by appropriate means carried on the haven. While a two-cable cableway provided increased stability for personnel carrier, it was more expensive than a single cable and, further, it was difficult to maintain the same tension in both cables of a two-cable cableway. Without the same tension, one cable will sag below the other with consequent undesirable leaning of the carrier. Additionally, the provision of means on the haven for tensioning the cableway is unnecessary in most installations because suitable tensioning means usually are readily available on the platform. In the patented system, however, a floating haven was fixedly anchored near, but at a safe distance from, the production platform. At least one cableway unsupported between its ends was attached to and extended above the water between the platform and the haven, with the cableway inclining downwardly from the platform to the haven. A personnel carrier was suspended from and was movable along the cableway for transferring personnel from the platform to the haven. The haven included at least one upright buoyant cylinder and means for ballasting and deballasting the cylinder. Means also defined an enlarged watertight compartment mounted to the upper end of the cylinder with the top of the compartment forming a weather deck. The cylinder and the compartment-defining means together formed a structure ballastable to float with the compartment partly submerged for increased stability. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
U.S. Pat. No. 4,527,503 patented Jul. 9, 1985 by R. F. Connelly provided a span buoy escape system for offshore platforms. The safety system included an offshore platform supporting personnel above the surface while it extends below the surface of the sea. A floatable escape vessel in the form of a spar buoy was mounted on the platform approximately at sea level. When dismounted from the platform, the escape vessel was ballast controllable such that a substantial amount of the entire vessel was below sea level to provide stability as a floating vessel. The top of the upper portion was openable and included means by which the personnel may enter the top portion from the platform and travel to the lower portion. The escape vessel was mounted on the platform at a location from which it could be dismounted into the sea after receiving the personnel. A compartment was provided in the lower portion of the spar buoy and a winch was mounted in the compartment. An anchor was located on the seabed. A tether connected the anchor and the winch and operated within the spar buoy to control the length of the tether between the anchor and the winch to permit the spar buoy to float at the surface of the sea above the anchor. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
U.S. Pat. No. 4,646,929 patented Mar. 3, 1982 by B. P. Plissoneau et al, provided a basket for life-saving use at sea, which could be used from a boat or a helicopter. The patented life-saving basket included a plurality of parallel horizontal frame elements connected to at least two U-shaped hoops arranged in planes perpendicular to the planes of the frame elements to form mesh sides of the basket. The bottom of the basket was provided with longitudinal elements forming supports. Each hoop was connected to each frame at each point of intersection by a separate connecting element. The free ends of each hoop and those of two handle elements of inverted U-form were joined by a top edge frame which included two longitudinal members on which are engaged, spaced by distance pieces. The free ends of the hoops and the handle elements, and two transverse members connected to the ends of the longitudinal members. This patent suffered from the deficiency that its structure was not sufficiently rigid to protect persons being transported. A problem also exists in the excessive swinging of the harness-net device in high wind conditions.
U.S. Pat. No. 4,652,246 patented Mar. 24, 1987 provided a life net to rescue men from sea or water on board a ship or upon a pier. The patented rescue net structure for rescuing persons from the sea or other bodies of water had a net with mesh openings which were larger than thigh size but which were smaller than chest size. The net was attached to side ropes which were provided with floats. The side ropes at a forward end of the structure were extended to form pulling ropes. A sinker rope extended between the side ropes at the rear end of the structure. The sinker rope had the effect of submerging the rear end of the structure in the water, and pulling together rear end portions of the side ropes while their front ends remain open. Thus a partial enclosure was formed into which a person to be rescued can enter and be enmeshed in the net in an upright position. This patent suffered from the deficiency that its structure was not sufficiently rigid to protect persons being transported. A problem also exists in the excessive swinging of the harness-net device in high wind conditons.
A problem also inherent on those systems which employed a helicopter, e.g., U.S. Pat. No. 4,627,821, was that the cable means for suspending the device from a helicopter, had to be arranged to allow easy entry of the device over a flotation ring. The cable means were fixed to the deck and fixed or limited in movement relative to the ring so that when the device was lifted by the cable means the major lifting forces were transmitted to the deck while the ring was held a predetermined distance above the deck.
U.S. Pat. No. 2,471,544 patented May 31, 1949 by G. A. Ring, provided means for connecting mooring cables to rotary winged aircraft. In operating a helicopter from the deck of a ship, it was found that the pitching and rolling movements of the ship relative to the helicopter may be such as to cause landing to become difficult or dangerous. If such relative motion was great at the moment landing is effected, the forces resulting therefrom may produce destructive stresses in the helicopter. The patented device included means for connecting a mooring or landing cable to rotary winged aircraft. A guide cable was secured to the aircraft at two points spaced laterally from a vertical line passing through the center of gravity thereof. A pair of pulleys was also secured to the aircraft for guiding the guide cable, the pulleys being spaced from the points and lying on the opposite side of the vertical line. The guide cable was longer than a line passing from one of the points through the pulleys and back to the other of the points. A landing cable carriage was mounted upon the guide cable at a pair of points lying between the pulleys and the points. This system suffered the deficiency that it was only operative against the lift of a helicopter and could not be used for hauling down a personnel transfer chamber.
Landing a helicopter on a small deck, particularly on a ship, can be a very difficult and tricky operation. To minimize accidents, this was usually accomplished with the aid of a securing system in which a haul-down cable was attached to the helicopter, usually after being obtained from the deck by a messenger cable lowered by the helicopter. A deck-mounted winch is then used to haul-down the helicopter to the deck level and to secure it.
One difficulty with systems of this type was that, while they adequately and safely pulled the helicopter down to the deck, they did not provide sufficient lateral support for the helicopter while it was on the deck and during the last few feet of descent impart severe side loads to the helicopter. Some auxiliary arrangement must therefore be used to laterally-secure the helicopter on the deck, or the risk of damage through lateral movement must be borne.
One technique for hauling down and securing such helicopter is shown in U.S. Pat. No. 3,392,940, Jul. 16, 1968, by J. F. Van Valkenburg. The patent provided an apparatus for automatically anchoring or securing a drone or other type of helicopter to the surface on which it lands. The improved anchoring apparatus included a drum assembly, a first cable system that extended from a first fixed point on the drum assembly along one edge of the landing surface back to a second fixed point on the drum assembly, a second cable system that extended from a third fixed point on the drum assembly along the opposite edge of the landing surface back to a fourth fixed point on the drum assembly, means for controlling rotation of the drum assembly, and means for maintaining portions of the cables along opposite sides of the landing surface in parallel until a predetermined amount of tension is applied to the cables. This system suffered the deficiency that it was only operative against the lift of a helicopter and could not be used for hauling down a personnel transfer chamber.
In U.S. Pat. No. 3,801,050, patented Apr. 2, 1974, by W. N. Stone, a system was provided for hauling-down and securing a helicopter or the like with a haul-down cable loop which attached at one point to the helicopter and at another point to a deck winch. The cable loop passed through the deck at two separate locations via swivel sheaves so that while the helicopter was being hauled-down, the cable acted like a single cable, exerting a downward force and, after the helicopter was on the deck, exerted both vertical and lateral forces to secure the helicopter on the deck. The cable looped over a draw sheave below deck, which was connected to the winch by a draw line so that the haul-down cable was free to run over the draw sheave to equalize tension during haul-down. After landing, the sheaves and cables would be locked by suitable braking means so that the two cables from the helicopter to the deck-mounted sheaves could restrain the helicopter.
Canadian Patent Number 610,617 patented Dec. 13, 1960 by W. T. Rollings, provided a two-stage air-cushion device for absorbing the shock of a load falling to the ground, comprising an upper air cushion, a lower air cushion, and a platform interposed between the cushions for supporting the load, the lower cushion being collapsible upon striking the ground. Means was provided for inflating the upper cushion by air forced from the lower cushion by its collapse on the ground, the upper cushion then pressing upwards against the load and cushioning the latter in relation to the platform. This system suffered the deficiency that it was only operative against the lift of a helicopter and could not be used for hauling down a personnel transfer chamber.
U.S. Pat. No. 3,912,192 patented Oct. 14, 1975 by A. J. W. Shirley, provided a restraining device for holding objects in position on the deck of a moving craft, particularly for holding aircraft in position on the deck of a ship. The device was of the type comprising a spring-loaded drum capable of turning in a mounting and carrying a strop or similar flexible member for connection to the object to be held, the unwinding of which was resisted by the spring. The improvement of the invention consisted of a ratchet control mechanism including a ratchet wheel truning with the drum and acted on by a pawl controlled by a hydraulically-damped pendulum so as to be moved into engagement with the ratchet teeth when the pendulum was swinging through more than a predetermined angle from the vertical. As long as the deck was substantially horizontal, the aircraft or object would be held in position by means of strops from at least three of the restraining devices, but it would nevertheless be possible to move the aircraft as required by extending one or more of the strops against the effect of its spring and allowing the remaining strop or strops to be taken up under spring control. On the other hand, as soon as the deck of the craft tilted beyond the predetermined angle to the horizontal, the pendulum would move the pawls into engagement with the ratchet teeth, preventing the drum from rotation and thus holding the aircraft firmly in position. A manually-controlled pawl could also be provided so as to lock the drum against rotation even when the deck was horizontal.
Launching systems for life support capsules are required to be both rugged and yet simple and reliable in operation. It is important that they be capable of lowering a life support capsule into the sea off of a derrick or offshore oil rig without the necessity of human attention on the rig. Since the capsules have a considerable weight, it is important that the descent of the capsule to the surface of the water be controlled. Since such system should be designed for use primarily in emergency conditions, it was important that it function smoothly and properly with a minimum of attention. Capsule launch systems have been provided which utilized a combination of hydraulic cylinders and movable sheaves. While such systems were generally satisfactory, they were characterized by high cost. Hydraulic cylinder rods were subject to corrosion and high maintenance and repair costs. Also changes in temperature had a greater affect on lowering rate due to changes in hydraulic fluid viscosity. Further, since the hydraulic fluid used to operate the system usually was inflammable, and the hoses and other connections were subject to damage, the hydraulic system could be rendered useless in the event of a fire or extreme heat. Winches with centrifugal brake energy absorbers have been used in launch systems but experienced problems with heat dissipation and wear at brake surfaces when subjected to relatively high loadings and large descent heights.
U.S. Pat. No. 3,702,690 patented Nov. 14, 1972 by W. T. Higgins, provided a launching system which was said to be useful for raising and lowering life support capsules and the like from offshore drilling rigs, in which the capsule was lowered by a winch at a controlled rate as regulated by a centrifugal blower operated through speed-up gearing. In the patented system, a disk brake on the blower shaft holds the life support capsule in any given position. Provision was included for releasing the brake at a remote point, such as within the capsule, to provide for an unpowered and controlled descent. The brake was connected through a one-way clutch so that the capsule may be raised by the rotation of the winch while the brake is on to prevent accidental descent of the capsule. An electric motor was provided for raising the capsule by the winch, and is isolated by means of a clutch which works on an operator common with that of the brake to assure that the motor is declutched prior to releasing the brake, in a lowering operation. Provision was included for raising the capsule by hand, and also for manually retrieving and paying out the cable when the capsule was not attached.